TITLE: CO + H Sub 2 Reaction over Nitrogen-Modified Iron Catalysts.  Quarterly Technical Progress Report, October 1, 1983-December 30, 1983.

AUTHOR: W. N. Delgass.

INST.  AUTHOR: Purdue Univ., Lafayette, IN.

SPONSOR: Department of Energy, Washington, DC.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  Feb 84,  31p.

ABSTRACT:

The synthesis of epsilon-Fe/sub 2.7/N is confirmed by Moessbauer spectroscopy. Carburization of epsilon-iron nitride for 2.5 hours in 3H sub 2 /CO at 523 K starts the formation of a bulk structure similar to that seen during gamma '-iron nitride carburization. Reaction of gamma '-Fe sub 4 N in 3CO/H sub 2 synthesis gas at 523 K shows a better bulk stability than reaction in 3H sub 2 /CO. Kinetic analysis of the product distribution at the higher CO ratio confirms greater activity and selectivity maintainance. The kinetics of denitriding in both He and H sub 2 was studied with a mass spectrometer. Extremely rapid nitrogen loss was observed from both gamma '-Fe sub 4 N and epsilon-Fe/sub 2.7/N catalysts in H sub 2 at 523 K. In both cases a initial exposure to H sub 2 produced a significant amount of NH sub 3 which we ascribe to an active surface species. Hydrogenation of the bulk continued with a slow rise to a maximum about 90 seconds after the introduction of H sub 2 . The denitriding activity of the epsilon-Fe/sub 2.7/N catalyst was significantly higher than that of the gamma '-Fe sub 4 N catalyst. In contrast, the denitriding rate of epsilon-Fe/sub 2.7/N in He was significantly slower than that in H sub 2 until high temperatures (773K) were reached. An overall activation energy of 41.5 kcal/mol was obtained for this process. Comparison of the denitriding rate of virgin epsilon-Fe/sub 2.7/N in H sub 2 with that of the same nitride after five minutes of carburization during the hydrocarbon synthesis reaction indicates large differences in the overall rate. The carburized nitride was some 300 times less active to bulk hydrogenation than the virgin catalyst, which is indicative of significant changes in the first few layers of the nitride during the initial minutes of the synthesis reaction. 17 references, 5 figures. (ERA citation 09:018310)

REPORT  NUMBER: DOE/PC/50804-5

CONTRACT  NUMBER: FG22-82PC50804